ArrayData Enumeration for Primitive, Binary and UTF8 (#3749)

* Add BooleanBuffer

* Add NullBuffer

* Add PrimitiveArrayData

* Add BytesArrayData

* Move module

* Make private for now

* Move NullBuffer to arrow-buffer

* Format

* More docs

* Seal traits

* Doc

* Review feedback

arrow-buffer/src/buffer/boolean.rs

@@ -0,0 +1,84 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use crate::{bit_util, Buffer};
+
+/// A slice-able [`Buffer`] containing bit-packed booleans
+#[derive(Debug, Clone)]
+pub struct BooleanBuffer {
+    buffer: Buffer,
+    offset: usize,
+    len: usize,
+}
+
+impl BooleanBuffer {
+    /// Create a new [`BooleanBuffer`] from a [`Buffer`], an `offset` and `length` in bits
+    ///
+    /// # Panics
+    ///
+    /// This method will panic if `buffer` is not large enough
+    pub fn new(buffer: Buffer, offset: usize, len: usize) -> Self {
+        let total_len = offset.saturating_add(len);
+        let bit_len = buffer.len().saturating_mul(8);
+        assert!(total_len <= bit_len);
+        Self {
+            buffer,
+            offset,
+            len,
+        }
+    }
+
+    /// Returns the number of set bits in this buffer
+    pub fn count_set_bits(&self) -> usize {
+        self.buffer.count_set_bits_offset(self.offset, self.len)
+    }
+
+    /// Returns `true` if the bit at index `i` is set
+    ///
+    /// # Panics
+    ///
+    /// Panics if `i >= self.len()`
+    #[inline]
+    pub fn is_set(&self, i: usize) -> bool {
+        assert!(i < self.len);
+        unsafe { bit_util::get_bit_raw(self.buffer.as_ptr(), i + self.offset) }
+    }
+
+    /// Returns the offset of this [`BooleanBuffer`] in bits
+    #[inline]
+    pub fn offset(&self) -> usize {
+        self.offset
+    }
+
+    /// Returns the length of this [`BooleanBuffer`] in bits
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.len
+    }
+
+    /// Returns true if this [`BooleanBuffer`] is empty
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.len == 0
+    }
+
+    /// Returns the packed values of this [`BooleanBuffer`] not including any offset
+    #[inline]
+    pub fn values(&self) -> &[u8] {
+        &self.buffer
+    }
+}

arrow-buffer/src/buffer/mod.rs

@@ -25,7 +25,10 @@ pub use immutable::*;
 mod mutable;
 pub use mutable::*;
 mod ops;
+pub use ops::*;
 mod scalar;
 pub use scalar::*;
-
-pub use ops::*;
+mod boolean;
+pub use boolean::*;
+mod null;
+pub use null::*;

arrow-buffer/src/buffer/null.rs

@@ -0,0 +1,90 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use crate::buffer::BooleanBuffer;
+
+#[derive(Debug, Clone)]
+pub struct NullBuffer {
+    buffer: BooleanBuffer,
+    null_count: usize,
+}
+
+impl NullBuffer {
+    /// Create a new [`NullBuffer`] computing the null count
+    pub fn new(buffer: BooleanBuffer) -> Self {
+        let null_count = buffer.len() - buffer.count_set_bits();
+        Self { buffer, null_count }
+    }
+
+    /// Create a new [`NullBuffer`] with the provided `buffer` and `null_count`
+    ///
+    /// # Safety
+    ///
+    /// `buffer` must contain `null_count` `0` bits
+    pub unsafe fn new_unchecked(buffer: BooleanBuffer, null_count: usize) -> Self {
+        Self { buffer, null_count }
+    }
+
+    /// Returns the length of this [`NullBuffer`]
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.buffer.len()
+    }
+
+    /// Returns true if this [`NullBuffer`] is empty
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.buffer.is_empty()
+    }
+
+    /// Returns the null count for this [`NullBuffer`]
+    #[inline]
+    pub fn null_count(&self) -> usize {
+        self.null_count
+    }
+
+    /// Returns `true` if the value at `idx` is not null
+    #[inline]
+    pub fn is_valid(&self, idx: usize) -> bool {
+        self.buffer.is_set(idx)
+    }
+
+    /// Returns `true` if the value at `idx` is null
+    #[inline]
+    pub fn is_null(&self, idx: usize) -> bool {
+        !self.is_valid(idx)
+    }
+
+    /// Returns the inner buffer
+    #[inline]
+    pub fn inner(&self) -> &BooleanBuffer {
+        &self.buffer
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_size() {
+        // This tests that the niche optimisation eliminates the overhead of an option
+        assert_eq!(
+            std::mem::size_of::<NullBuffer>(),
+            std::mem::size_of::<Option<NullBuffer>>()
+        );
+    }
+}